(19)
(11) EP 0 558 172 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
07.12.1994 Bulletin 1994/49

(43) Date of publication A2:
01.09.1993 Bulletin 1993/35

(21) Application number: 93250061.4

(22) Date of filing: 22.02.1993
(51) International Patent Classification (IPC)5: G05D 11/13
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 27.02.1992 US 843624

(71) Applicant: ISCO, Inc.
Lincoln Nebraska 68504 (US)

(72) Inventors:
  • Jameson, Daniel Gene
    Nebraska, 68502 (US)
  • Allington, Robert William
    Nebraska, 68502 (US)

(74) Representative: UEXKÜLL & STOLBERG 
Patentanwälte Beselerstrasse 4
22607 Hamburg
22607 Hamburg (DE)


(56) References cited: : 
   
       


    (54) Multiple solvent delivery system and method


    (57) To control a solvent composition in a supercritical fluid system, a first pump pumps a first solvent through a first conduit into a mixer and a second pump pumps a second solvent through a second conduit into the mixer. First and second transducers measure the pressure in the first and second conduits and generate first and second signals proportional to the pressures. Each pressure signal is multiplied by a corresponding programmed concentration signal and compared to the programmed pressure in a feedback system to generate an error signal. The error signal is multiplied by concentration signals from a programmer to control the pumping rate of each pump. The pumps pressurize each fluid one at a time at the start of a run. The pressurization process is also used for producing disturbance-free flow as delivery is changed from one pump to another during prolonged runs.






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